Very true. I always tell my friends that it's only junk if you can't use it. I try to focus on using the rares in my binders and then uncommons that are necessary for the decks. I've got gallon sized ziplock bags of basic lands and non-rare cards in my 800-count boxes. I almost don't want to randomly donate them because some cards do gain value out of nowhere.
While there will always be cards that are initially overlooked at first or don't prove useful until something complimentary gets printed, it's still relatively easy to makes some huge cuts to your collection.
Yoked Ox is very, very, very unlikely to ever become valuable. I keep exactly one copy of a lot of cards because another tribal bear with first strike isn't going to make my deck, same thing with yet another reprint of
Divination. At most, I may have 4 cards in a set that I keep extra copies of because I think they may have some potential to creep up. There are some that are kind of obvious, like
Mystic Sanctuary. While I don't think it will ever be $20, a couple extra copies so I don't end up paying $2.50 in 5 years to get back something I gave away for free is worth the extra space. Most deal X damage red instants and sorceries are interchangeable,
Abrade was worth keeping some extra copies of [though more for non-EDH]. The hard ones to evaluate are the cards that do something totally different but don't seem to have much use, at least not yet.